It is printed on your KTTW card (gold status), but we also found the need to remind the CMs in the shops on some occasions. We had one situation of "That adds to XYZ" and I asked if he had taken the platinum discount--no, he'd not done that "yet." At that point, it was not automatic; the CM had to manually enter the discount.
Do be aware that there are some items which are not eligible for the discount.